A device for loading and unloading a tray of a freeze drying plant is known from EP 1 619 459 A1, the pusher apparatus thereof including a bar that is adapted for upward and downward pivotal movement and that is retained on a carriage guided on the right and on the left side of the transfer table and on the tray. The carriages are guided on special rails which are attached to the right and left edge of the transfer plate and of the tray. The rails are configured to be a web protruding upwards at right angles and concurrently forming a lateral limitation for the vials located on the transfer table or on the tray.
To load the tray with a number of vials, said vials are at first placed onto the transfer table. As soon as there are enough vials on the table, the bar retained on the carriages is brought to the foremost vials, a flexible metal tape being attached to a respective one of the right and left carriages and being actuated through a drive. Then, the bar is moved further in the direction of the tray, thus pushing the vials in front of it. The rails, which act as a side limitation, hereby ensure that no vials will fall down from the transfer table or from the tray. As soon as the foremost vials have been placed onto the tray, the metal tapes pull the carriages, and as a result thereof the bar, back into the initial position before the bar is pivoted away upward through a pivoting mechanism mounted to the carriage for the next vials to be passed underneath the bar and be placed onto the transfer plate. At the same time, the now filled tray is moved upward in the freeze drying plant and the next, empty tray is provided. If enough vials are on the transfer table, this process is repeated and the pusher device pushes the next group of vials onto the next tray.
For unloading, the bar is again travelled upward through the pivoting mechanism and, through the flexible tapes, is brought together with the carriage as far as the rear edge of the tray where the bar is lowered again. Then, the tapes are pulled tight again, thus pulling the carriage and the bar together with the vials from the tray onto the transfer table from where the vials are then evacuated.
Upon pushing the vials from the transfer plate onto the tray, it may happen that the vials, which had originally been placed correctly in discrete rows, get disarranged, some vials also being brought as far as the rail confining them laterally. If the number of vials continues to be pushed onto the tray, the outer vials are caused to touch the rail, the vials getting even more disarranged due to the occurring friction. Some vials may also tumble.
Upon completion of the freeze drying process, the pusher apparatus is moved as far as the rear border of the tray by means of the carriages guided on the rails. Often, the carriage needs to push vials located close to the rail slightly aside in order to arrive at the rear end of the tray. Hereby, the vials are even further disarranged and discrete vials can tumble.
During unloading, the vials are now at first pushed together in analogous fashion in the opposite direction and are moved from the tray onto the transfer table. Again, a friction occurs between the outer vials and the rail confining the sides so that the vials get even more disarranged and that a vial may tumble.
Moreover, it happens that some vials get stuck on the underside of the tray located above after the freeze drying process. If now the pusher device is introduced with the bar into the freeze drying plant, the bar hits the vials sticking on the underside of the next tray; as they fall down, these vials can tip over.
Food or drugs are often processed in freeze drying plants. As a result, the hygiene requirements are very demanding. As a result, tipped over vials are not allowed to be processed further and constitute scrap material.